Selective remote position control servosystem



July 10, 1962 1 M. LUNN ET AL 3,043,998

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SELEOTIVE: REMOTE POSITION CONTROL sERvOsYsTEM July 10, 1962 2 Sheets-Sheet 2 Filed Oct. 3, 1960 SWS .6 RUD Wm OLLU N T .EA R mMmV O ESE ,T Wc .D T .INL A ESC M REN WMA AAE Y .I .JJ E# United States Patent Oilce 3,043,998 Patented July 10, 1962 3,043,998 SELECTIVE REMOTE POSITION CUNTROL SERVSYSTEM Lawrence-M. Lutin, .lames L. Shields, and Jean C. lDe Vault, all of Linton, Ind. Filed Oct. 3, 1960, Ser. No. 60,097 2 Claims. (Cl. 318--29) 'I'he present invention relates to an electromechanical control system for accurately and automatically positioning or repositioning a rotating device to any one of a plurality of predetermined azimuth settings, and has more particular reference to an improved control system for accurately and automatically positioning or repositioning an antenna to a predetermined azimuth setting.

There are presently used several methods in positioning a television antenna to a predetermined azimuth setting. In one method, the antenna is rotated independently of the step of selecting a channel on the television set. There may be provided a mechanical linkage Ifor achieving the rotation of the antenna.

Another known method of achieving independent rotation of a television antenna, is to provide a manually controlled hydraulic control valve for a hydraulic rotor device to which the antenna is connected.

A further known method of providing independent rotation of a television antenna is by an electric motor used to rotate the antenna in which the motor is controlled :for positioning to the best relative reception by an electric directional switch located in the vicinity of the television receiver.

This known arrangement may include a stepper switch controller for setting manually the desired relative direction or position of the antenna, and the controller trains the antenna to that position.

It has been found that each of the known methods is inaccurate and the best azimuth setting cannot be mechanically achieved on successive operations. Generally, the operator is usually required to physically observe the `training of the antenna to assure that the best azimuth position is achieved.

Accordingly, the present invention is directed to a television receiver antenna which is automatically and accurately oriented and positioned by an electromechanical control system throughout the 360 rotation thereof on successive operations and in which the signal strength reception of any fixed radiating source is optimum, since the electromechanical control system of the invention accurately resets the position of the antenna to a preset position for reception of the optimum signal strength.

The invention also seeks to provide a novel electromechanical control system for positioning an antenna with respect to any of several fixed radiation sources for optimum signal strength reception.

Basically, the present invention provides a novel and improved electromechanical control system for a rotatable receiving antenna, in which the operation of the electromechanical control system may be coupled to a receiver channel selector and the control system is provided with a bridge circuit having an A.C. source Aconnected thereto, one branch. of the bridge circuit being adjusted by the relative position of said antenna and the other branch of said bridge circuit being adjusted by the position of said channel selector to unbalance the bridge circuit, a phase sensitive means responsive to the unbalance condition of the bridge circuit, a control means responsive to the phase sensitive means `for detecting the amount of unbalance of the bridge circuit, and a motor operated by the control means for driving the antenna to a new position in which the branches of the bridge circuit are balanced and no unbalanced condition is present in the phase sensitive means.

Therefore, it is the object of the invention to provide an electromechanical control system in which a balanced condition in a bridge circuit is used to maintain an antenna in a receptive position and in which any unbalanced conditions are detected torreposition the antenna to a predetermined azimuth setting that balances the bridge circuit.

It is another object of the invention to provide a bridge circuit of the control system which includes impedance elements that may be adjusted to new values with respect to the balanced condition of the bridge circuit, and thus it is possible to adjust the balance of the bridge circuit so that new predetermined azimuth settings may be easily achieved.

A complete understanding of the invention may be had from the following description of a particular en1- bodiment of the invention. In the description, reference is made to the accompanying drawings, of which:

FIGURE 1 is a block diagram of the electromechanical control system for repositioning a television receiving antenna in accordance with a preferred embodiment of the present invention; and

FIGURE 2 is a detailed circuit diagram of the electromechanical control system of FIGURE 1.

Referring now to the drawings, an A.C. power source 10 is connected to the convenience outlet of a conventional television receiver (not shown) so that the power source 10 is electrically energized by the ON position of the oil-on switch of the receiver.

The A.C. power source 10 includes a transformer 12 having secondaries 14 and 16 and having a grounded center-tapped secondary 18. The voltage induced in secondary 14 is applied through a motor control switch 20 to a rotor motor 22; the voltage induced in secondary 16 is sullicient to energize the lament circuits of tubes 24, 26, 28; and the voltage induced in the secondary 18 is a single phase alternating current supply for the plates of the tubes 24, 26, 28, as well as a supply for a bias supply 30.

The power source 10 includes a transformer 32 having a secondary 33 from which power is applied to an A C. bridge circuit formed by a first branch 34 and a second branch 36.

The `A.C. power source 10 is seen as a phase synchronizing reference and energy supply for both the A.C. bridge and a phase detector 38 formed by the circuit arrangement of tubes 26, 28. The A C. power source 10 may be used for the motor 22, or any other convenient A.C. source suitable to the motor may be used.

The rst branch 34 of the bridge circuit includes a potentiometer 40 having the ends thereof connected to the secondary 33 and the adjustable sliding contact 42 connected to ground.

The second branch 36 of the bridge circuit comprises a parallel arrangement of a plurality of potentiometers 51, '52, 53, 54, 55, 56', 57, 58, 59, 60, 61, 62, each having adjustably preset contacts 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82. The number of potentiometers 51 to 62 is equal to the number of receivable channels of the television receiver (not shown).

The adjnstably preset contacts 71 to 82 are connected to respective contacts 91 to 102 of a bridge resistance selection switch 104. The switch has a rotatable switching element 106 connected by mechanical coupling 105 to a tuner or channel selector switch (not shown) of the receiver. In this way, the channel selector switch is set manually to a desired channel and the related potentiometer 51 to 62 has its adjustably preset contact connected through the bridge resistance selection switch 104.

Initially, the contacts 71 to 82 have been preset by adjustment until optimum reception is obtained in thevreceiver by the position of the antenna.

The channel selection switch and the bridge resistance selection switch 1G4- are set to another channel and the respective potentiometer is adjusted for optimum reception in the receiver. Once the potentiometers are each adjusted to correspond with an appropriate desired position of the antenna, then selection of a desired channel by the channel selector switch automatically positions the antenna for optimum strength reception by the unbalanced condition of the bridge establishing an AC. signal voltalge output of the bridge circuit. The output of the bridge circuit may be of insufficient amplitude, so it is fed to a grid of tube 24 of a signal amplifier 110. The amplified signal is taken from the plates of the tube 24 and applied respectively and simultaneously to the control grids of thyratron tubes 26 and 2% which form a portion of a phase detector 3? through coupling network 112, 114.

The plates of the thyratron tubes 26, 28 receive their plate energy from secondary 18, one plate being out-ofphase with the other to provide a reference for phase difference detection.

The direction in which the bridge circuit is unbalanced determines which thyratron tube 26, 2S has a signal applied to its respective grid in an in-phase condition. The irl-phase condition exists when a thyratron tube has both the plate and the grid thereof energized positive with respect to the cathode, the cathode being tied directly to ground. As a result of the positive in-phase condition, the thyratron tube conducts or iires to cause sufficient current flow in its plate circuit to energize the respective relay 120, 122 in its plate circuit forming a portion of the motor control switch 20.

The other thyratron tube will have a negative plate voltage and a positive grid voltage, or a positive plate voltage and a negative grid voltage thereon, and will not tire to energize its circuit connected relay.

The relays 120, 122 control respective contact switches 124, 126 energized by the secondary 14 to thereby apply the desired phased energy to the rotor motor 22.

The shaft of the rotor motor 22 is directly coupled, or coupled through `desired gear reducing means (not shown), to an antenna shaft 128 to rotate an antenna 132. As the antenna is rotated by the motor 22, a mechanical coupling 130 tied to the antenna shaft 12S adjusts or moves the sliding contact 42 along the potentiometer 40 until a null condition eXists in the branches 34, 36 of the bridge circuit.

In the event the other thyratron tube had tired, the opposite direction of rotation of the antenna shaft 123 and movement of contact 42 would be obtained until the balance of the branches 34, 36 of the bridge circuit is achieved.

After the bridge circuit achieves the null or balanced condition, there no longer is any unbalanced condition to establish a signal to trigger either of the thyratron tubes 26, 28, and the antenna remains in the position, which position is the optimum position for signal reception of the receiver as has been preset in the adjustment of potentiometers 51 to 62.

In order to optimize the stability of the phase detector 38, the thyraton tubes are biased considerably more negative than the breakdown point for selected AC. plate voltage so that there must be substantial or discernible input signals applied to the grids of the tubes 26, 28 to render them conductive. The required bias for this ses purpose is obtained from a bias supply 30 connected to secondary ld and is controlled in magnitude by a sensitivity control potentiometer 134.

lt is, of course, within the contemplation of the present invention to use any appropriate types of thyratron tube for those shown in FIGURE 2. A transformer may be conveniently used to replace the amplifier 110 and transistors may be substituted for any or all of the tubes 24, 2d, 2S. Also, saturable transformers may be conveniently substituted to replace the tubes.

Additional embodiments of the invention in this specification will occur to others and therefore it is intended that the scope of the invention be limited only by the appended claims and not by the embodiment described hereinabove. Accordingly, reference should be made to the following claims in determining the full scope of the invention.

What is claimed is:

l. A remote control antenna positioning system for a television receiver having a channel selector and a rotating television receiving antenna comprising an A.C. source of current supply, a bridge circuit having said A.C. source connected thereto, a first branch of said bridge circuit having a variable impedance element varied by the relative position of said receiving antenna, a secondbranch of said bridge circuit being preselectedly adjusted by the position of said channel selector of said receiver, phase sensitive means connected to the output of the bridge circuit and responsive to the unbalance of current in said bridge circuit, relay control means connected to the phase sensitive means for detecting the amount of unbalance of current in said bridge circuit, a motor connected to the relay control means for rotating said receiving antenna and adjusting the variable irnpedance element until the bridge circuit is rebalanced.

2. A remote control antenna positioning system including a position selector switch for a rotatable television receiver antenna comprising an A.C. source of current supply, a bridge circuit having said A C. source connected thereto, a first branch of said bridge circuit having its impedance value adjusted by the relative position of said receiver antenna a second branch of said bridge circuit having its impedance value adjusted by the position of said position selector switch, phase sensitive means connected to the bridge circuit and responsive to the unbalance of current in said bridge circuit, control means connected to the phase sensitive means for detecting the amount of unbalance of current in said bridge circuit, a motor connected to the control means for rotating said receivnig antenna and adjusting the impedance of said first branch until the bridge circuit is rebalanced, and a bias control means to adjust the action of oper* ability ofthe phase sensitive means.

References Cited in the file of this patent UNITED STATES PATENTS 2,443,347 Field June 15, 1948 2,535,147 Markusen Dec. 26, 1950 2,671,877 Stewart Mar. 9, 1954 2,725,519 Malick et al Nov. 29, 1955 2,790,121 Martin Apr. 23, 1957 2,796,567 Boode fune 1S, 1957 2,830,244 Davis Apr. 8, 1958 2,889,507 Kennedy et al. June 2, l959 2,914,717 Redding Nov. 24, 1959i 2,944,202 Bonacorsi July 5, 1960 

